Accelerator pump system

ABSTRACT

A fuel valve that is urged toward its seat by gravity is located in the discharge passage of a carburetor accelerator pump and separates the discharge passage from an outlet passage communicating directly with the carburetor induction passage. An air vent is provided for the outlet passage and a check valve located in the air vent also is urged toward its seat by gravity. During accelerator pump operation, the air vent check valve remains on its seat and fuel flows into the carburetor induction passage. If a low pressure develops in the outlet passage, the pressure differential lifts the air vent check valve from its seat before the fuel valve is lifted from its seat and thereby prevents spurious fuel flow through the accelerator pump system.

im States i! atent 1 1 Bishop Jan. 29, 1974 Ford Motor Company, Dearbom,Mich.

Filed: Mar. 2, 1972 Appl. No.: 231,298

Inventor:

Assignee:

Primary ExaminerTim R. Miles [57] ABSCT A fuel valve that is urgedtoward its seat by gravity is located in the discharge passage of acarburetor accelerator pump and separates the discharge passage from anoutlet passage communicating directly with the car- 52 US. Cl 261/34 Aburetor induction P g An air vent is Provided for [51] Int. Cl. F02m7/08 the Outlet p g d a check valve ed in th air 58 Field of Search261/34 A vent also is urged toward its seat y y- During accelerator pumpoperation, the air vent check valve [56] References Cit d remains on itsseat and fuel flows into the carburetor UNITED STATES PATENTS inductionpassage. If a low pressure develops in the outlet passage, the pressuredifferential lifts the air 2 vent check valve from its seat before thefuel valve is 2:920:877 1/1960 Spragle 67 lifted from its seat andthereby prevents spurious fuel 1,923,429 8/1933 Ericson 261 34 A flowthrough the accelerator P p y 2,267,57O 12/1941 Markham... 261/34 A3,460,813 8/1969 Hieger 261/34 A 3 Clam, 1 D'awmg Flgure 34 if 32 K 22 Z1 I as r28 4 36 24 &

Tfi 190 Z \/f z 4 ACCELERATOR 1P SYSTEM SUMMARY OF THE INVENTION Duringcertain periods of reciprocating engine operation, a pressuredifferential is transmitted through the induction passage of thecarburetor and into the discharge passage of the carburetor acceleratorpump system. The pressure differential draws fuel through theaccelerator pump system and into the engine. For many years thissituation was ignored since the amount of fuel was small and it hadminimal effect on engine performance and fuel economy. Investigationsinto engine exhaust emissions revealed, however, that such fuel pulloverseriously affects the quantitity of various compounds in the engineexhaust gases. An attempt at solving the pullover proposed locating aspring loaded fuel valve in the accelerator pump discharge passage, butsubsequent analysis showed that the force produced by the springnecessary to prevent pullover also produced an undesirable delay inaccelerator pump operation.

This invention provides an accelerator pump system that positivelyprevents both fuel pullover through the induction system and direct fuelloss to the atmosphere. The pump system has a fuel check valve locatedwhere the discharge passage of the accelerator pump opens into an outletpassage that communicates directly with the carburetor inductionpassage. An air vent mechanism communicates with the outlet passage andincludes a check valve permitting air flow into the outlet passage butpreventing any flow out of the outlet passage. When the system is atrest the air vent check valve is urged toward its seat by a force thatis considerably less than the force urging the fuel check valve towardits seat.

. During accelerator pump operation, fuel pressure produced by theaccelerator pump moves the fuel check valve from its seat and forcesfuel into the outlet passage. Any resulting pressure increase in theoutlet passage increases the seating force on the air vent check valveto prevent positively any fuel leakage through the air vent. Fuelreaching the outlet passage flows into the carburetor induction passagefrom which it is drawn into the engine. If engine operation produces alow pressure in the outlet passage, the air vent check valve opens tobleed off the low pressure. Both the fuel check valve and the air ventcheck valve conveniently are urged toward the respective valve seat bygravity. The fuel check valve is designed with greater mass or smallerpressure area than the air vent check valve to insure that the air ventcheck valve opens when low pressure exists in the outlet passage.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a achematicillulstration of an accelerator pump system of the invention. Both theair vent check valve and the fuel valve of the illustration are urged bygravity to the closed position.

DETAILED DESCRIPTION Referring to the drawing, a fuel source 10, whichcan be the fuel bowl of a conventional carburetor, has an opening 12 inits floor through which fuel flows to the inlet of an accelerator pumpindicated generally by numeral 14. A ball type valve 16 serves as theinlet to accelerator pump 14. The accelerator pump piston 18 is mountedslidably in a chamber and is connected to the throttle linkage (notshown) for appropriate reciprocating motion.

A discharge passage 20 connects the pump chamber defined in part by ballvalve 16 and piston 18 with an outlet passage 22. Passage 20 issubstantially vertical at its opening into outlet passage 22 and a fuelvalve 24 is located in the opening so that gravity urges the fuel valveonto a seat 26. When the fuel valve 24 is on its seat 26, the valveprevents any fuel flow from passage 20 into passage 22.

Passage 22 communicates directly through a discharge nozzle 28 with aninduction passage 30 of the carburetor. Induction passage 30 is aportion of the induction system of the engine (not shown). Passage 22also communicates through a vent mechanism 32 with the atmosphere or avelocity pressure area of induction passage 30. Vent mechanism 32comprises a ball type check valve 34 that is urged onto a seat 36 bygravity. Check valve 34 has substantially less mass than fuel valve 24.

When accelerating fuel is required by the engine, piston 18 movesdownward to force a fuel charge against the lower surface fo fuel valve23. The fuel charge lifts valve 24 from its seat, which permits the fuelto flow past the valve and into outlet passage 22. A slight pressureincrease occurs in passage-22 and the pressure increase assists inholding ball valve 34 on its seat. The fuel reaching passage 22 thusflows through nozzle 28 and into induction passage 30.

Low pressure produced during some engine operating modes at nozzle 28can be transmitted into outlet passage 22 where the low pressure tendsto lift fuel valve 24 from its seat and draw fuel from passage 20. Underthese circumstances, ball valve 34 is lifted from its seat prior to anysignificant movement of fuel valve 24. Air thus is drawn through thevent mechanism into passage 22 to dissipate the low pressure,

Passage 22 preferably slopes upward between fuel valve 24 and air ventcheck valve 34 to inhibit any tendency for fuel to collect around theair vent check valve. Small amounts of fuel might collect around the airvent check valve under certain conditions but the fuel usually is drawnback into passage 22 without escaping into the atmosphere. If necessary,the vent mechanism can communicate with passage 22 through the roof ofpassage 22.

Fuel valve 24 and air vent check valve 34 can be spring loaded towardthe respective valve seats if desired. In this arrangement, the springfor air vent check valve 34 produces a lower force than the spring forthe fuel valve to insure that the air valve opens when low pressureexists in outlet passage 22. Nozzle 28 preferably is as close aspossible to fuel valve 24 to reduce the time required for fuel to reachinduction passage 30.

Thus this invention provides an accelerating pump system for preventingfuel pullover into the induction system and preventing fuel leakage intothe atmosphere. Since the relative opening resistance of the air ventcheck valve and the fuel valve determines proper system operation, theactual opening resistance of the fuel valve can be low to reduce fuelflow delay.

I claim:

ll. In a fuel supply system for an engine including a fuel source and aninduction passage, an accelerator pump system comprising,

pump means obtaining fuel from said fuel source,

passage means connected to said pump means for transmitting fuel fromsaid pump means to said induction passage,

a fuel valve urged toward its seat by gravity and located in saidpassage means for controlling fuel 5 flow from said pump means to saidinduction passage, said fuel valve opening when said pump means isactuated, and

vent means for venting the portion of said passage means downstream ofsaid fuel valve, said vent means including a check valve movableindependently of the fuel valve permitting air flow into the passagemeans through the vent means but preventing fuel flow out of the passagemeans through the vent means, said check valve being urged toward itsseat by gravity to close the vent and having a mass less than the massof the fuel valve so as to be lifted off its seat to an open poisitionprior to said fuel valve when a predetermined subatmospheric pressureexists in the portion of the passage means downstream of the fuel valve.

2. The fuel supply system of claim 1 in which the passage meanscomprises an outlet passage communicating directly with said inductionpassage and a pump discharge passage connecting said pump means withsaid outlet passage, said fuel valve being located at the junction ofsaid pump discharge passage with the outlet passage, and said air ventcheck valve communicating with said outlet passage.

3. The fuel supply system of claim 1 in which the passage meanscomprises an outlet passage communicating directly with said inductionpassage and a pump discharge passage connecting said pump means withsaid outlet passage, said fuel valve being located at the junction ofsaid pump discharge passage with the outlet passage, and said vent meanscommunicating with said outlet passage.

1. In a fuel supply system for an engine including a fuel source and aninduction passage, an accelerator pump system comprising, pump meansobtaining fuel from said fuel source, passage means connected to saidpump means for transmitting fuel from said pump means to said inductionpassage, a fuel valve urged toward its seat by gravity and located inSaid passage means for controlling fuel flow from said pump means tosaid induction passage, said fuel valve opening when said pump means isactuated, and vent means for venting the portion of said passage meansdownstream of said fuel valve, said vent means including a check valvemovable independently of the fuel valve permitting air flow into thepassage means through the vent means but preventing fuel flow out of thepassage means through the vent means, said check valve being urgedtoward its seat by gravity to close the vent and having a mass less thanthe mass of the fuel valve so as to be lifted off its seat to an openpoisition prior to said fuel valve when a predetermined subatmosphericpressure exists in the portion of the passage means downstream of thefuel valve.
 2. The fuel supply system of claim 1 in which the passagemeans comprises an outlet passage communicating directly with saidinduction passage and a pump discharge passage connecting said pumpmeans with said outlet passage, said fuel valve being located at thejunction of said pump discharge passage with the outlet passage, andsaid air vent check valve communicating with said outlet passage.
 3. Thefuel supply system of claim 1 in which the passage means comprises anoutlet passage communicating directly with said induction passage and apump discharge passage connecting said pump means with said outletpassage, said fuel valve being located at the junction of said pumpdischarge passage with the outlet passage, and said vent meanscommunicating with said outlet passage.